[Gutter] Factor out method to set common gutter component properties

src/custom-gutter-component.coffee

@@ -1,3 +1,5 @@
+{setDimensionsAndBackground} = require './gutter-component-helpers'
+
 # This class represents a gutter other than the 'line-numbers' gutter.
 # The contents of this gutter may be specified by Decorations.
 
@@ -33,15 +35,7 @@ class CustomGutterComponent
     decorationState = state.gutters.customDecorations[@getName()]
     @oldState ?= {}
 
-    # TODO (jessicalin) Factor this out (also in LineNumberGutterComponent).
-    # Also, set backgroundColor?
-    if gutterProps.scrollHeight isnt @oldState.scrollHeight
-      @decorationsNode.style.height = gutterProps.scrollHeight + 'px'
-      @oldState.scrollHeight = gutterProps.scrollHeight
-
-    if gutterProps.scrollTop isnt @oldState.scrollTop
-      @decorationsNode.style['-webkit-transform'] = "translate3d(0px, #{-gutterProps.scrollTop}px, 0px)"
-      @oldState.scrollTop = gutterProps.scrollTop
+    setDimensionsAndBackground(@oldState, gutterProps, @decorationsNode)
 
     return if !decorationState
 

src/gutter-component-helpers.coffee

@@ -0,0 +1,16 @@
+# Helper methods shared among GutterComponent classes.
+
+module.exports =
+  # Sets scrollHeight, scrollTop, and backgroundColor on the given domNode.
+  setDimensionsAndBackground: (oldState, newState, domNode) ->
+    if newState.scrollHeight isnt oldState.scrollHeight
+      domNode.style.height = newState.scrollHeight + 'px'
+      oldState.scrollHeight = newState.scrollHeight
+
+    if newState.scrollTop isnt oldState.scrollTop
+      domNode.style['-webkit-transform'] = "translate3d(0px, #{-newState.scrollTop}px, 0px)"
+      oldState.scrollTop = newState.scrollTop
+
+    if newState.backgroundColor isnt oldState.backgroundColor
+      domNode.style.backgroundColor = newState.backgroundColor
+      oldState.backgroundColor = newState.backgroundColor

src/line-number-gutter-component.coffee

@@ -1,4 +1,5 @@
 _ = require 'underscore-plus'
+{setDimensionsAndBackground} = require './gutter-component-helpers'
 
 WrapperDiv = document.createElement('div')
 
@@ -30,17 +31,7 @@ class LineNumberGutterComponent
 
     @appendDummyLineNumber() unless @dummyLineNumberNode?
 
-    if @newState.scrollHeight isnt @oldState.scrollHeight
-      @lineNumbersNode.style.height = @newState.scrollHeight + 'px'
-      @oldState.scrollHeight = @newState.scrollHeight
-
-    if @newState.scrollTop isnt @oldState.scrollTop
-      @lineNumbersNode.style['-webkit-transform'] = "translate3d(0px, #{-@newState.scrollTop}px, 0px)"
-      @oldState.scrollTop = @newState.scrollTop
-
-    if @newState.backgroundColor isnt @oldState.backgroundColor
-      @lineNumbersNode.style.backgroundColor = @newState.backgroundColor
-      @oldState.backgroundColor = @newState.backgroundColor
+    setDimensionsAndBackground(@oldState, @newState, @lineNumbersNode)
 
     if @newState.maxLineNumberDigits isnt @oldState.maxLineNumberDigits
       @updateDummyLineNumber()